Information is communicated in a communication system between a sending station and a receiving station by way of a communication channel. The sending station includes at least a transmitter for transmitting an information-containing, communication signal to the receiving station. And, the receiving station includes at least a receiver for receiving the communication signals transmitted thereto.
A radio communication system is a type of communication system. In a radio communication system, the communication channel forming a link between the sending and receiving stations is formed of a portion of the electromagnetic frequency spectrum. Unlike conventional, wireline communication systems, no fixed or hard-wired connection is required to form the link between the sending and receiving stations. Therefore, when the use of a fixed or hard-wired connection between the sending and receiving stations would be inconvenient or impractical, a radio communication system is particularly advantageously utilized.
Communication of the information between the sending and receiving stations may be effectuated by formatting the information into packets of data. Once formatted into packets, the information can be transmitted to the receiving station in discrete bursts, formed of a single packet, or a series of packets, to the receiving station. Packet data communications are sometimes effectuated in a radio communication system.
A Mobitex (tm) communication system is a type of radio communication system in which packet data communications are effectuated. In such a system, a base station forming a portion of a Mobitex network transmits packets of message data on downlink channels to selected, remotely-positioned mobile radio modems. A Mobitex system is a multi-user system in which, typically, large numbers of remotely-positioned, radio modems are capable of receiving packets of message data. Once significant amounts of data are to be communicated to a mobile radio modem, sequences of packets of message data are transmitted to the modem. Each time in which a mobile radio modem receives a packet of message data, the radio modem acknowledges reception of such packet. Such acknowledgment is made by transmitting back to the Mobitex network an acknowledgment signal. Detection at the Mobitex network of the acknowledgment signal indicates to the network not only that the packet has been received but also that the radio modem is in an active state.
Transmission difficulties might prevent the reception at the mobile radio modem of the packets of message data transmitted thereto. The mobile radio modem may, for instance, be carried to a position whereat the radio modem is unable to receive properly the packets of message data transmitted thereto. When, for example, the radio modem is carried into the interior of a building structure, the building structure might significantly attenuate the packets of message data transmitted by the base station of the network portion, thereby to prevent the radio modem from receiving the packets.
When the mobile radio modem fails to receive the packets of message data, the radio modem fails to send an acknowledgment response back to the network portion. In at least one Mobitex system, once a selected number of packets of message data transmitted to a mobile radio modem are not acknowledged to have been received there at, the modem is considered to be inactive and further communications of message data to the radio modem are at least temporarily halted.
However, if the radio modem is only temporarily positioned beyond the coverage area of the Mobitex system, the network might prematurely determine the radio modem to be inactive. If the radio modem is thereafter repositioned at a location in which message data transmitted by the Mobitex network can once again be received by the radio modem, a premature determination that the radio modem is inactive prevents the efficient communication of message data to the radio modem.
A manner by which the activation status of the radio modem can be more accurately determined would therefore be beneficial. A mobile radio modem, or other receiving station, positioned only temporarily beyond the coverage area of a sending station, such as a base station of a Mobitex network portion of a Mobitex system would thereby be less likely to be determined prematurely to be inactive.
It is in light of this background information related to communication systems in which packets of data are transmitted between sending and receiving stations that the significant improvements of the present invention have evolved.